The present invention relates to a method for preventing erythropoietin in an aqueous solution from being adsorbed on the inner surface of the wall of a container. The invention also relates to an erythropoietin composition so formulated as to avoid the adsorption of erythropoietin onto the inner surface of the wall of a container.
Erythropoietin is a circulating glycoprotein that stimulates the formation of red blood cells and is useful in the treatment or diagnosis of anemia. A single dose of erythropoietin is as small as a few micrograms and this level must be strictly observed. In other words, erythropoietin must be administered in the accurate trace amount in which it is formulated in a dosage form.
However, it has been observed that erythropoietin in an aqueous solution adsorbs on the inner surface of the wall of a glass or plastic container, and the amount that is actually administered is significantly smaller than the amount initially formulated in a dosage form. For example, when an aqueous solution of erythropoietin is charged into a glass or plastic container for transfusion, a considerable amount of erythropoietin is adsorbed on the inner surface of the container wall and this is more likely to occur with lower concentrations of erythropoietin than higher concentrations. Erythropoietin which must be administered in a trace amount has a great chance of adsorption on the inner surface of the wall of a container and because of the smallness of the amount in which it is initially incorporated, the loss of erythropoietin due to adsorption is substantial, causing a significant decrease in the dose that can be actually administered. The necessary and accurate amount of erythropoietin could be dissolved in aqueous solution by taking great care to avoid any adsorption of the erythropoietin on the inner surfaces of the wall of containers and other devices used in the preparation of aqueous erythropoietin solutions. However, when the aqueous solution of erythropoietin is transferred into a glass or plastic syringe for actual administration or if it is injected into a glass or plastic container for mixing with a transfusion solution, a substantial portion of erythropoietin is adsorbed on the inner surface of the wall of the syringe or container, causing serious problems for therapeutic purposes.
Under these circumstances, the present inventors made various studies to develop a method for preventing erythropoietin in aqueous solution from being adsorbed on the inner surface of the wall of a container.